Congratulations and beautiful area! I love the Riviera Maya!
We too are having a long engagement. It will be two years. A little less than a year and a half left, now!
We knew, even before getting engaged, that we were going to have a destination wedding, and we have been completely upfront about that to our friends and family since day 1. For us, we needed to get married during summer months (I'm a teacher... built in time off), and one year wasn't enough time to save up enough money. Some people have really appreciated the early notice.... even if they do not go, they know about it and can book vacation time and save money if needed.
We made a website and forwarded it to our close friends and family, but we have to wait a bit longer still before booking for sure... As soon as we book, we are sending out save the dates. Then, about 8 months out or so, we will send out invitations. At least, that is the plan.
Some people will respond negatively to different aspects of your wedding. I have heard some pretty nasty stuff about having a long engagement, and, even moreso, about having a destination wedding. But, by being completely upfront about it since the beginning, we can always say, "Well, it's not like they didn't know...." lol. People who want to be there will, if possible, make the effort to start saving money and such. Other people won't.
I definitely don't think it is too early to start looking at stuff. I have been making a few things and picking up odds and ends here and there.... and looking at lots of pictures! Enjoy your engagement... it is somewhat stressful, but SO much fun too!
I only hope I continue to say that over the next year and a half!